Fluid couplings are commonly used in concert with flexible, elastomeric hoses to communicate fluid pressure between locales or to fluidly connect sources for the purpose of transporting fluid therebetween. Fluid couplings have broad utility across many industries relating to a wide variety of applications. Such couplings—typically connected by a flexible conduit or hose to form a hose assembly—are particularly useful in applications where one source may be moveable, or subject to vibration relative to another portion of a system, and where rigidly connected conduits may be compromised by such movement or vibration. Hose assemblies are commonly found in mobile machinery, electric power, refinery, mining and construction equipment industries. The equipment used in these industries often includes multiple instances where hose assemblies are employed to transport fluid (gaseous or liquid) commonly under high pressure and elevated temperature. Common examples of hose assembly usage in the mobile machinery and electric power industries include: connecting a high pressure hydraulic fluid source to pressure cylinders to animate implements, transporting fuel from a source to a fuel system within a combustion engine, communicating lubrication oil from a supply to moving or engaging parts such as, for example, gears in a transmission, transporting coolant from a source to a heat transfer element such as a radiator to cool the fluid and communicating fluid between pump/motor assemblies to transform fluid pressure to rotary motion.
A common form of fluid coupling includes a metallic stem portion which is structured to receive an end of a flexible elastomeric hydraulic hose and a metallic shell portion, which surrounds the hose, has inwardly directed barbs and is structured to provide a tight collar vis-à-vis the hose portion sandwiched between the stem and shell.
Although not part of the fluid coupling assembly, the hose is an element of the completed hose assembly and is commonly reinforced with a metallic wire weave or winding sandwiched between an inner elastomeric liner in concentric relation with an outer elastomeric cover portion to form a hose that is constructed to withstand high temperature and pressure application. A hard plastic sheath, overlaying and encasing the outer cover portion of the hose, may be provided to reduce damage caused by impact and abrasion related contact to the hose.
A common method to permanently affix the hose end with the coupling entails sliding the hose onto the stem of the coupling and thereafter deforming the metallic shell portion of the coupling via dies on a hydraulic press, for example, in order for the barbs of the shell to concentrically crush the hose between the shell and stem. This process is commonly referred to as “crimping” or “swaging”. There are two common types of couplings termed “skive” and “no-skive” couplings. As it relates to the skive coupling, the coupling assembly is not structured to address the cover of the hose. Therefore, the cover, including the outer abrasion resistant sheath if one exists, must be removed prior to the swaging operation to ensure that the barbs within the shell provide an adequate measure of compression to the reinforcement wire and the liner of the hose. As it relates to the non-skive coupling, the coupling assembly is structured to address (e.g., penetrate) the cover of the hose, thus little if any preparation to the hose is required and the cover does not need to be removed prior to the swaging operation. The barbs of the non-skive coupling are structured to penetrate the cover to provide a sufficient measure of compression to the reinforcement wire and the liner in sealing the liner with the stem. Non-skive couplings are typically preferable because the additional steps to remove the cover add expense and difficulty to the assembly process.
Unfortunately, hose assemblies heretofore utilizing swaged couplings may be subject to leakage and shortened life due to “over-compression” of the hose liner material in the vicinity of the barb tip. The swaging operation imparts a significant radial load that acts substantially along a circumferential line on the liner. At the site of the liner/barb interface and accompanying liner/stem interface, the elastomeric liner is often subject to complete compression—meaning the liner is completely compressed and is incompressible (e.g., a solid). In this state, the liner has little or no resiliency and as the liner wears any significant temperature or pressure variation may cause the liner to lose its seal with the stem resulting in premature leakage and shortened life. In response to this situation, fluid couplings employ multiple rows of barbs axially spaced within the shell to decrease the likelihood of fluid leaking past the multiple seals in serial arrangement.
As it relates to manufacturing and assembling the coupling assembly with the hose resulting in a finished hose assembly, manufacturers often suggest employing specialized equipment to provide a precisely swaged connection between the coupling assembly and hose. Since the goal in ensuring a fluid tight seal is to compress the hose liner near the barb tip to the point of incompressibility of the hose there is little if any margin for error when the shell of the coupling assembly is undergoing permanent deformation. In fact, near the point that the hose becomes incompressible any additional compression by the swaging device may cause deformation of the shell and stem resulting in scrapped parts, premature leakage or shortened life of the hose assembly at a significant expense. As a result, many hose assemblies are scrapped during the swaging process and it is not uncommon for the hose assembly to leak if the proper equipment has not been employed and proper procedures have not been meticulously followed.
U.S. Pat. No. 6,447,017, to Gilbreath et al. issued Sep. 10, 2002 discloses a fluid coupling assembly employing a stem and shell combination that is swaged to sandwich a reinforced hose member therebetween. The stem is serrated, including a series of spaced grooves and the shell includes a plurality of spaced barbs. Radial displacement of the barb ends, caused by the swaging operation, displaces the reinforcement wire of the hose to substantially compress or “pinch” the liner material against the stem to form a generally circumferentially linear seal directly under each barb. Some barbs are positioned to overlay grooves of the stem and others may be positioned to overlay higher portions or “lands” on the stem. In some instances, the liner directly under each barb is compressed along a circumferential line on the stem to the point it is near “incompressibility” along this line and in other instances the barb may not adequately interact with the groove to provide an adequate seal. The overly compressed liner portions may be subject to premature leakage or shortened life when the liner is subject to natural degradation, thermal cycling or axial movement of the hose relative to the coupling assembly due to pressurization.
A fluid coupling which may overcome one or more of these limitations and one that would be readily manufacturable would be desirable. Furthermore, a non-skive fluid coupling assembly which does not significantly add cost relative to known fluid couplings, and one which may be readily adaptable to available reinforced hose members to form hose assemblies is highly desirable.